This section provides background information related to the present disclosure which is not necessarily prior art.
Scroll-type compressors typically include two scroll components having involute portions or vanes which are intermeshed together to define sealed pockets. One of the scroll components orbits with respect to the other scroll component, so that the pockets are progressively reduced for compression. For optimum performance, a scroll compressor design should minimize leakage, wear, and fracture. Scroll components of scroll compressors are frequently manufactured by a molten metal process (“casting”). For conventional methods of casting scroll components, a molten metal is poured into a cavity defined by a casting mold assembly, where the molten metal solidifies and forms a scroll after solidification is complete.
In casting processes, mold assemblies (including molds and optionally cores) into which the molten metal flows are frequently composed of sand, binder, and/or a ceramic coating and may not have full structural rigidity. In sand casting, generation of loose sand and other debris can occur to due high velocities and abrupt changes in direction and turbulence of the molten metal. The narrow and deep space of the involute portions or vanes of the scroll component are especially susceptible to entrapping foreign material such as loose sand that might be carried along with the molten metal. The orientation of the involute portion in the mold assembly is a factor in this susceptibility, because the long, narrow regions of the involute portion can be a trap for debris. It is desirable to minimize casting tolerances and sand-related quality problems such as scabs, inclusions and blow-holes. Furthermore, the involute portions of the scroll component are susceptible to having a temperature below a target pour temperature during casting and thus being undercooled, which has the potential to form undesirable graphite forms, defects, and/or other undesirable metal microstructures. Thus, when cast in conventional processes, the involute portions of the scroll component having such issues can have greater susceptibility to fracture or early failure.
Furthermore, in many applications, the scroll components formed from casting are subsequently extensively machined to precise tolerances. It would be desirable to minimize the extent of machining required for cast scroll components. Further, it is desirable that the scroll components formed from casting are substantially free of defects, undesirable graphite species, and/or undesirable microstructures. Casting methods are needed that can efficiently and inexpensively form high quality, low defect scroll components.